It's no doubt
impressive when today's compact sedans -- which are loaded down with
hundreds of pounds of safety gear and chassis reinforcements not
found on vehicles from decades past -- top the 40 mpg mark. However,
it's even more impressive when midsize sedans approach that mark as
well.

You know about
the compact 2011
Chevrolet Cruze and 2011
Hyundai Elantra which can hit 40+ mpg on the highway. Hyundai's
2011 Sonata midsize sedan can achieve 35 mpg on the highway in its
base configuration. GM is now flaunting its 2012 LaCrosse which will
come standard with eAssist technology (which will provide up to 37
mpg on the highway) and will be priced at roughly $30,000.

“It’s a very
integrated powertrain system, with no compromises in driving
performance, shift quality or ride and handling,” said Daryl
Wilson, LaCrosse lead development engineer. “We believe this
combination points to the future of vehicles powered primarily by an
internal combustion engine.”

The LaCrosse
will be powered by a traditional 2.4-liter direct injection
four-cylinder engine which generates 180 hp. The engine is mated to a
6-speed automatic transmission. However, GM also includes its next
generation "mild hybrid" system which it calls eAssist. On
the LaCrosse, the eAssist electric motor provides an additional 15 hp
and 79 pound-feet of torque during acceleration. Other features to
improve fuel economy include an engine start/stop function and
regenerative braking.

A 115V
lithium-ion battery mounted in the trunk powers the electric motor,
but it encroaches on cargo-hauling capabilities. Maximum cargo
capacity drops from an already lackluster 13.3 cu ft to just 10.9 cu
ft.

However, the
benefits in fuel economy are huge. EPA ratings jump from 19/30 mpg
(city/highway) to an impressive 25/37 mpg. The city rating falls
short of Lincoln's
MKZ Hybrid which pulls in an impressive 41 mpg, but that vehicle
is priced higher at $35,180.

“The eAssist
system is more than just the next-generation BAS system. The ability
to integrate regenerative braking with the latest lithium-ion battery
technology creates a system that delivers significant fuel-efficiency
gains that customers will enjoy,” said Steve Poulos, global chief
engineer of the eAssist system. “Being able to provide electric
boost to the powertrain system during heavy acceleration and grade
driving enables the LaCrosse transmission to operate more
efficiently, while the added functionality of engine start-stop and
fuel shut-off during deceleration provides added fuel savings.”

Official pricing
and availability of the Buick LaCrosse with eAssist should be
available closer to its launch later next year.

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The last I've heard rechargeable lithium batteries have about 10x the base energy density of ultracaps. Even with hybrids only using a fraction of the total capacity in order to stretch the batteries lifetime over the lifetime of the car they'd still need to gain about 2.5x the capacity to be competitive in size and weight.